Sweating Bronze to Copper

I've sweated plenty of copper to copper but never bronze to copper. I'm trying to sweat a bronze shower drop elbo to copper pipe with little luck. I'm using regular lead free plumbing solder and flux. I'm cleaning the fitting and copper well with steel wool. I've tried my propane torch and MAPP gas torch for a bit more heat. Can't seem to get the solder to wick down into the joint and hold. Is there some special flux or solder that I need to use or some other secret?

The elbow is probably cast brass, but brass, bronze, or copper, it's all the same. A heavy fitting defintely requires you to put all the heat on the fitting and try to get it up to heat as quickly as possible so the flux doesn't burn. I assume this is a 1/2" fitting, so any of the torches you mentioned should do the job.